Mass spectrometers comprising a Liquid chromatography ion source are well known. Liquid chromatography is a method by which species from a mixture can be separated into their individual components. The basic components of a liquid chromatography system are a pumping system comprising at least two solvent channels and a tube filled with stationary phase and a column onto which components are initially trapped. By adjusting the percentage composition of the solvent channels, species are released from the stationary phase to be detected by various means at the column output.
The inside diameters of LC columns vary widely from, for example, <50 μm to >4.6 mm. The delivery flow rate required from the pumping system increases with the inside diameter of the column and ranges from several nanoliters per minute to several milliters per minute. To produce a gradient at a flow rate of several nL/min it is often necessary to split the delivery flow rate from a liquid chromatograph. The LC eluent may then pass to an Atmospheric Pressure Ionisation (“API”) ion source where a range of ionisation processes may occur. The ion source may, for example, comprise an Electrospray Ionisation (“ESI”) ion source, an Atmospheric Pressure Chemical Ionisation (“APCI”) ion source or an Atmospheric Pressure Photoionisation (“APPI”) ion source.
Electrospray Ionisation is a widely used technique in mass spectrometry in which species present in a flowing solution are ionised by the application of a high voltage. Electrospray is known as a soft ionisation technique because the resulting ions typically comprise relatively large molecular weight species (e.g. peptides) which can then be detected as intact ions by a mass analyser. Electrospray Ionisation can be achieved at several different flow rates ranging from several nL/min to several mL/min. The ion counts observed in a mass spectrometer during Electrospray Ionisation are not, to a first approximation, flow rate dependent and as such large sensitivity gains for the same signal to noise ratios can be achieved at lower flow rates due to much lower sample consumption.
The coupling of liquid chromatography and Electrospray mass spectrometry (LCMS) and tandem mass spectrometry (LCMS/MS) is a powerful technique that is widely used in many laboratories.
Mass spectrometers commonly comprise a sampling cone together with a cone-gas cone which forms the interface between the mass spectrometer and an ion source such as an Electrospray Ionisation ion source. A cone gas or curtain gas may be provided to the annulus between the inner sampling cone and the outer cone-gas cone. Ions which pass through the sampling cone are then transmitted through a first vacuum chamber and are transmitted onwardly through an extraction cone into a second vacuum chamber. Conventionally, the sampling cone, cone-gas cone and extraction cone are made from stainless steel. Stainless steel is considered to be relatively inert and non-reactive. However, conventional sampling cones, cone-gas cones and extraction cones need regular cleaning in order to maintain high performance.
Conventional sampling cones, cone-gas cones and extraction cones can suffer from increased surface contamination following regular analysis of complex matrix extracts such as urine, saliva, plasma, whole blood, waters and soils. In addition complex buffered eluent systems such as ammonium acetate, ammonium formate, sodium phosphate, sodium borate and sodium formate can also cause contamination. Other potential additives which can increase surface activity and/or contamination include formic acid, trifluoroacetic acid and ammonia.
It is desired to provide an improved sampling cone, cone-gas cone and extraction cone for a mass spectrometer. In particular, it is desired to provide a more robust sampling cone, cone-gas cone and extraction cone which is less reactive than stainless steel and which requires less intensive cleaning than conventional sampling cones, cone-gas cones and extraction cones.
Also well known are Mass spectrometers comprising a gas chromatograph coupled to an Electron Ionisation (“EI”) or Chemical Ionisation (“CI”) ion source are well known. A gas chromatograph comprises a packed column or open capillary tube located in a heated chamber. Analyte gas molecules are caused to pass through the column. Gas molecules having different sizes and structures will take different amounts of time to elute from the gas chromatograph.
Ions which emerge from the gas chromatograph are then commonly ionised either by an Electron Ionisation ion source or by a Chemical Ionisation ion source.
An EI ion source comprises an ion chamber through which an electron beam is passed. Analyte gas molecules interact with the electron beam and are subsequently ionised. The ionisation process is commonly referred to as being a hard ionisation process in that the analyte molecules are caused to fragment as a result of the ionisation process. The resulting EI fragment ions are then mass analysed.
A CI ion source utilises a reagent gas (e.g. methane or ammonia) and may be operated in either a positive or negative mode of operation. Neutral reagent gas is arranged to be ionised by interactions with free electrons emitted from a filament. The resulting reagent ions are then caused to interact and ionise neutral analyte molecules resulting in the formation of analyte ions. The resulting analyte ions are then mass analysed.
The coupling of a gas chromatography column with an EI or CI ion source and a mass spectrometer is a powerful technique that is widely used in many laboratories.
Conventionally, EI and CI ion sources comprise ion source chambers made from stainless steel. Stainless steel is considered to be relatively inert and non-reactive. However, conventional EI and CI ion source chambers need regular cleaning in order to maintain high performance.
Conventional EI and CI ion source chambers can suffer from increased surface contamination following regular analysis of complex matrix extracts such as urine, saliva, plasma, whole blood, waters and soils.